6 FARMERS’ BULLETIN 557. 
the best, means of preventing the escape of the gas is to line the fumi- 
gator with sheet tin, with soldered joints, and over sheathing. An- 
other method is to sheath the room inside, cover the walls, ceiling, 
and floor with tarred or heavy building paper, with joints well lapped, 
and cover the inside with matched ceiling boards. The fumigator 
should always be equipped with a tight door in which the joints have 
been broken, similar to the door of a refrigerator or safe, and should 
close with two refrigerator catches against a thick felt weather strip, 
which should render it practically gas-tight. Thus constructed it 
would furnish sufficient space for the fumigation of about 200 bushels 
of material. There would also be sufficient space for the application 
and diffusion of the carbon bisulphid, hydrocyanic-acid gas, or other 
fumigant from the top with a charge more than necessary for the 
quantity of potatoes treated. 
It sometimes happens that the price of potatoes is so low that 
the small grower can not well afford to expend the amount of money 
which would be necessary for the construction of a special fumigator. 
In such a case it would be advisable to use a barrel, preferably a large 
oil barrel, with a tight-fitting cover for fumigating. It is possible 
also to fumigate, but not thoroughly, piles of tubers by covering them 
as tightly as possible with canvas, such as 10-ounce duck or tarpaulin. 
PROTECTION OF THE FALL CROP AND SEED POTATOES. 
A special letter of warning against the ravages of the potato-tuber 
moth in the shape of a press notice has been sent broadcast to news- 
papers, as well as to others, throughout the country. The main facts 
in the case were founded on the.experience of Mr. Graf in his inves- 
tigations and in his dealings with the potato growers of southern Cali- 
fornia. Concisely stated, the warning is to enable potato growers to 
undertake special work with seed potatoes and with the fall crop. 
For the protection of potatoes in fall against this pest it is urged 
that potato growers sort the potatoes for seed two weeks after digging 
and again two weeks later. The uninfested tubers should then be 
placed in a moth-proof bin. The infested tubers may be readily 
picked out because of the excrement of the larvee which adheres by 
webbing to the outer skin of the potatoes. The tubers in the moth- 
proof bin, after final sorting, should be fumigated with carbon bisul- 
phid (bisulphid of carbon) to destroy any moths which might have 
bred out or have obtained entrance through other means. Growers 
should now keep a careful lookout both in the field and among 
the fumigated tubers. At first those which have been fumigated 
should be inspected daily. Afterwards observations may be made 
every other day until finally once a -week will suffice. If there 
should be any indication that the tuber moth is propagating, a second 
fumigation is in order. 
